Emmanuelle Guillon

Characterisation of bimetallic platinum systems: application to the reduction of aromatics in presence of sulfur

Abstract Hydrogenation activity in presence of sulfur has been studied for bimetallic Pt–Ge/Al2O3 and Pt–Pd/Al2O3 systems. It has been shown that addition of germanium to platinum decreases the rate of aromatic hydrogenation whereas the palladium–platinum system exhibits higher activity. On the basis of a precise description of physico-chemical properties of bimetallic particles (characterisation by TEM, EXAFS, LEIS, TPR), a concept of sulfur resistant catalyst is discussed taking into account each actor in the catalytic process and their role in the modification of the active site properties.

A new synthetic route to produce metal zeolites with subnanometric magnetic clusters

By using a Co layered silicate as a source of Co and SiO(2), Co-Beta and Co-ZSM-5 zeolites with tetrahedrically coordinated cobalt were synthesized. Subnanometric clusters of Co can be produced and a magnetic material with superparamagnetic-paramagnetic phase transition is obtained.

Synergetic Effects in intimate Mixtures of PT/ZSM-48 and PT/ZSM-22 Zeolites in Bifunctional Catalytic Chain Branching of n-alkanes

ZSM-22 and ZSM-48 are aluminosilicate zeolites with tubular 10-ring pore systems. In their acid form and loaded with a trace of Pt metal, these zeolites are excellent catalysts for the skeletal isomerization of n-alkanes. With bifunctional catalysts, the yield of skeletal isomers from an n-alkane is limited because of the occurrence of cracking reactions consecutive to isomerization. We discovered that by physically mixing Pt/ZSM-22 and Pt/ZSM-48 zeolites, the yield of skeletal isomerization of octadecane can be increased by ca. 9% at the expense of cracking. The gain is entirely due to an enhanced yield of multibranched isomers. The synergetic effect can not be explained simply by an additivity of the specific isomers formed on the individual zeolite phases. The synergism is most likely due to the additional multibranching pathways that become available when departing from the monobranched skeletal isomer fractions that are differently composed on the respective zeolites.

Influence of zeolite structure on the performance of heavy reformate transalkylation catalysts

Conversion of ethylbenzene (EB) and commercial heavy reformate has been studied on different acid zeolite catalysts. The studied zeolites included topologies with channel systems containing 10 MR, 12 MR and 10+12 MR, namely ZSM-5, IM-5, mordenite, mazzite, Beta, NU-87 and ITQ-23. It has been found that zeolite structure has a direct influence in the ethyl dealkylation and transalkylation activity, increasing the dealkylation activity and selectivity when decreasing the zeolite pore volume. Zeolites NU-87 and ITQ-23 with 10×12 MR pores present an intermediate behavior from that of 10 and 12 MR pore zeolites. It has been also observed that ethylbenzene undergoes different bimolecular reactions involving for each reaction different biphenylic transition states.

Dry gel conversion synthesis of zeolite EU-1 from low alkali containing precursors

Abstract Zeolite EU-1 has been synthesized by dry gel conversion starting from low alkali containing precursors. A detailed study comparing this synthesis method to alkali-rich precursor systems and a classical hydrothermal synthesis has been achieved. A low alkali content extends composition ranges for zeolite EU-1 formation whereas the “dry” synthesis enhances conversion and the crystalline fraction of final products.

A new methodology to characterize the porosity of Y zeolites by liquid chromatography

Liquid chromatography breakthrough curves have been used to characterize the porosity of a dealuminated Y zeolite, and more precisely the mesopores in cavities and the cylindrical mesopores. The methodology presented in this paper shows that the use of several probe molecules with different molecular size and adsorption strength can give an estimation of the zeolite porosity.